1. Field
The present disclosure relates to a device for regulating stiffness, and more particularly, to a device for regulating stiffness by transmitting a rotational driving power of a driving motor to a rotary shaft connected to a driven member while maintaining predetermined stiffness.
2. Description of the Related Art
A rotating structure, which includes a driven member connected to a rotary shaft and a driving motor for rotating the rotary shaft so that the driven member is rotated, is used in various fields.
For example, the rotating structure may be easily found at a robot manipulator or the like and also used for treatment such as joint rehabilitation when a joint is damaged by an accident or the like.
FIG. 1 is a schematic view showing an example of a conventional rotating structure.
As shown in FIG. 1, if a joint portion 4 of the leg 1 of a patient is damaged and needs to be rehabilitated, a support member 5 is fixed to the thigh 2, and a driven member 6 hinged by the support member 5 is fixed to the calf 3. At this time, a hinge connection portion 7 between the support member 5 and the driven member 6 is fixed to the corresponding location of the joint portion 4.
A rotary shaft (not shown) is formed at one end of the support member 5 located at the hinge connection portion 7, and a driving motor 8 is connected to the rotary shaft.
If the rotary shaft rotates by the driving motor 8, the driven member 6 rotates on the hinge connection portion 7 with respect to the support member 5 by means of the rotating force of the rotary shaft. If the driven member 6 is rotated, the calf 3 fixed to the driven member 6 also rotates on the joint portion 4 accordingly.
If the driven member 6 is repeatedly rotated in clockwise and counterclockwise directions by adjusting a driving direction of the motor 8, the motion of bending and spreading the leg 1 may be performed repeatedly, and this motion helps rehabilitation of the damaged joint portion 4.
However, as shown in FIG. 1, if the rotating force of the driving motor 8 is directly transmitted to the rotary shaft which rotates the driven member 6, the rotating movement of the driven member 6 is entirely restricted by the driving power of the driving motor 8, which is called a rigidly coupling state. In other words, if the driving motor 8 starts driving, the driven member 6 also instantly rotates, and unless the driving motor 8 stops driving, a rotating force is continuously applied to the driven member 6.
The joint portion 4 of a person is an organ which operates by soft muscle contraction. If the joint portion 4 of a person moves by using a rotating structure in a rigidly coupling state as described above, the joint portion 4 may not follow the movement of the driven member 6, which may run the risk and damage the joint portion 4.
In addition, the damaged joint portion 4 may be hardened and immovable in a moment. At this time, unless the driving power of the driving motor 8 is intercepted instantly, the rotating force of the driving motor 8 may move the joint portion 4 constrainedly and give a great damage to the joint portion 4. The above phenomenon may also occur when the calf 3 cannot rotate any more due to an obstacle or the like.
Meanwhile, even when the above rotating structure is used for a robot manipulator (when the support member and the driven member are respectively robot arms), if the safety of the robot is considered, the stiffness of the rotary shaft and the driving motor for rotating a driven member needs to be suitably adjusted, as well known in the art.
As described above, when transmitting power of the driving motor and the rotary shaft, their stiffness should be suitably adjusted. For this, a stiffness generating device capable of generating desired stiffness may be used for adjusting the stiffness.
However, a conventional stiffness generating device changes stiffness by using an electromagnetic configuration as disclosed in Patent Literature 1, which however has a complicated design and is not easily controlled.